Preparation of Fibrous ZrO<sub>2</sub> and CaO-ZrO<sub>2</sub> from Zirconium Alkoxide by Sol-Gel Method

Abstract

The Zr(O-nC3H7)4 and Ca(CH3COO)2⋅H2OH2O-C2H5OH-HCl solutions were prepared and heated at 80°C for hydrolysis-condensation reaction of the alkoxide. The spinnability of the solutions was examined in the course of reaction. Following results have been obtained.(1) The Zr(O-nC3H7)4 solutions with the H2O/alkoxide molar ratio ranging from 0.7 to 1.5 and C2H5OH/alkoxide molar ratio larger than 4 exhibited spinnability within 2 to 9 hours. The ZrO2 gel fibers were successfully drawn.The CaO-ZrO2 gel fibers could also be drawn from the corresponding alkoxide-acetate solution with H2O/alkoxide molar ratio of about 1 and C2H5OH/alkoxide ratio of 27.(2) The solution composition region for spinnability is considerably limited, compared to the cases of making SiO2 and TiO2 gel fibers from Si(OC2H5)4 and Ti(OC3H7)4 solutions.(3) Transformation of the tetragonal ZrO2 to monoclinic ZrO2 occurring in ZrO2 fibers above 600°C caused the fracture of the fibers on heating. The addition of CaO to fibrous ZrO2 increased the stability of precipitating tetragonal ZrO2 and resulted in the avoidance of fracture of fibers by heating.(4) It is considered that the linear type zirconoxane polymers consisting of ZrO6 octahedra connected with each other by sharing their edges are formed in the spinnable Zr(O-nC3H7)4 solutions.